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Texture2D.cpp
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Texture2D.cpp
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#include "Texture2D.h"
#include <algorithm>
namespace {
bool is_power_of_2(int x) {
int cnt = 0;
while (x) {
x = x & (x - 1);
cnt++;
}
return cnt == 1;
}
}
void Texture2D::GenMipmap(void)
{
mips.push_back(texture);
glm::vec4 color[4];
for (int L = texture->GetWidth(); L > 1; L >>= 1) {
std::shared_ptr<Image> p = std::make_shared<Image>(L / 2, L / 2, texture->GetBpp());
for (int i = 0; i < L; i += 2) {
for (int j = 0; j < L; j += 2) {
mips.back()->read(i, j, color[0]);
mips.back()->read(i + 1, j, color[1]);
mips.back()->read(i, j + 1, color[2]);
mips.back()->read(i + 1, j + 1, color[3]);
glm::vec4 avg((color[0] + color[1] + color[2] + color[3]) / 4.0f);
p->write(i / 2, j / 2, avg);
}
}
mips.push_back(p);
}
}
bool Texture2D::EnableMipmap(void)
{
if (texture == nullptr
|| texture->GetHeight() != texture->GetWidth()
|| !is_power_of_2(texture->GetHeight()) )
return false;
is_mipmap_enable = true;
GenMipmap();
return true;
}
Texture2D::Texture2D()
: invW(0), invH(0), texture(nullptr)
{
wmode = WrapMode::Repeat;
smode = SampleMode::Nearst;
}
Texture2D::Texture2D(const char* file)
: texture(std::make_shared<Image>(file))
{
invH = 1.0f / texture->GetHeight();
invW = 1.0f / texture->GetWidth();
wmode = WrapMode::Repeat;
smode = SampleMode::Nearst;
}
namespace {
const std::vector<glm::vec4> TESTCOLORS{
{1.0f, 1.0f, 1.0f, 1.0f},
{1.0f, 0.0f, 0.0f, 1.0f},
{0.0f, 1.0f, 0.0f, 1.0f},
{0.0f, 0.0f, 1.0f, 1.0f},
{1.0f, 1.0f, 0.0f, 1.0f},
{0.0f, 1.0f, 1.0f, 1.0f},
{1.0f, 0.0f, 1.0f, 1.0f},
{0.4f, 0.4f, 0.4f, 1.0f}
};
}
const int Texture2D::GetWidth() const noexcept
{
return texture->GetWidth();
}
const int Texture2D::GetHeight() const noexcept
{
return texture->GetHeight();
}
glm::vec4 Texture2D::Sample(float x, float y, float level)
{
glm::vec4 color(0, 0, 0, 1);
if (wmode == WrapMode::Repeat) {
x -= std::floor(x);
y -= std::floor(y);
}
else {
// clamp to edge
x = std::min(1.0f - invW, std::max(invW, x));
y = std::min(1.0f - invH, std::max(invH, y));
}
if (is_mipmap_enable) {
level = std::max(0.0f, level);
int d1 = int(level);
int d2 = d1 + 1;
assert(d1 >= 0);
assert(d2 < mips.size());
#define MIPMAP_TEST
#ifdef MIPMAP_TEST
d2 = std::min(d2, 7);
d1 = std::min(d1, 7);
#else
d2 = std::min(d2, int(mips.size() - 1));
d1 = std::min(d1, int(mips.size() - 1));
#endif
float a = d2 - level;
float b = 1 - a;
#ifdef MIPMAP_TEST
glm::vec4 c1 = TESTCOLORS[d1];
glm::vec4 c2 = TESTCOLORS[d2];
#else
glm::vec4 c1 = BilinearSampling(mips[d1], x, y);
glm::vec4 c2 = BilinearSampling(mips[d2], x, y);
#endif
color = c1 * a + c2 * b;
}
else if (smode == SampleMode::Nearst) {
texture->read(x * texture->GetWidth() + 0.5f, (1 - y) * texture->GetHeight() + 0.5f, color);
}
else {
// smode == SampleMode::Bilinear
color = BilinearSampling(texture, x, y);
}
return color;
}
glm::vec4 Texture2D::BilinearSampling(std::shared_ptr<Image> src, float x, float y)
{
/*
dx = (a - c11) / (c21 - c11) , dy = (c - c11) / (c12 - c11)
c11---- a ---- c21
dy| | |
|------ c ----- |
| | |
| | |
c12---- b ---- c22
a = c11 + (c21 - c11) * dx;
b = c12 + (c22 - c12) * dx;
c = a + (b - a) * dy;
==>
c = (1 - dx)(1 - dy) * c11 + (1 - dx)dy * c12
+ (1 - dy)dx * c21 + dxdy * c22
*/
x = std::max(0.0f, x) * src->GetWidth() + 0.5f;
y = std::max(0.0f, 1 - y) * src->GetHeight() + 0.5f;
int x1 = std::min(src->GetWidth() - 1, (int)x);
int x2 = std::min(src->GetWidth() - 1, (int)(x + 1));
int y1 = std::min(src->GetHeight() - 1, (int)y);
int y2 = std::min(src->GetHeight() - 1, (int)(y + 1));
glm::vec4 colors[4];
src->read(x1, y1, colors[0]);
src->read(x2, y1, colors[1]);
src->read(x1, y2, colors[2]);
src->read(x2, y2, colors[3]);
float dx = (float)(x - x1);// / (x2 - x1); //around 1
float dy = (float)(y - y1);// / (y2 - y1);
glm::vec4 a = colors[0] + (colors[1] - colors[0]) * dx;
glm::vec4 b = colors[2] + (colors[3] - colors[2]) * dx;
return a + (b - a) * dy;
}